Within that sector of the packaging industry which deals with the packing of different types of liquids, such as milk, in consumer packages or cartons of paper and plastic laminate, use is occasionally made of packaging machines which reform prefabricated packaging container blanks into bottom-sealed packaging containers which are thereafter immediately filled with the intended contents and then sealed. In such an instance, the packaging container blanks are fed to the machine in the form of stacks of flat-laid tubular blanks which, prior to reforming into individual packaging containers, must be discharged one-at-a-time from an outlet or discharge end of the magazine. After the discharge from the magazine, the blanks are conveyed further in order to be raised, i.e. reformed into substantially quadratic cross section, and are placed on mandrels for further transport through different treatment stations in a per se known packaging and filling machine, it is, thus, of major importance that the blanks are actually discharged one-at-a-time from the magazine, which, in practice, has proved to be the source of considerable difficulties since the flat-laid blanks may not only display varying thickness, but may also have a certain tendency to spring up into their quadratic cross sectional state.
One prior art apparatus for discharging packaging container blanks from a magazine is described in European Patent No. EP-A-241.916, to which reference is now made. In this prior art apparatus, use is made of a horizontal magazine in which a stack of packaging container blanks is placed. At the discharge end of the magazine, there is a substantially vertically disposed reciprocating plate which displays an abutment facing towards the magazine, the thickness of the abutment being slightly less than the thickness of one flat-laid packaging container blank. When the plate is located proximal its upper, extreme position, the blank passes a separation gap where only one blank at a time may pass. Above the separation gap, there are provided a number of fingers which prevent the blank from accompanying the plate back in its downward return stroke.
Like other prior art apparatuses of a similar type, the above-described prior art apparatus for discharging flat-laid packaging container blanks displays an acceptable level of function and operational reliability when handling blanks which correspond to specification tolerances in all respects. However, since certain variations in the thickness of the flat-laid blanks cannot be completely avoided, it happens from time to time that two blanks accompany the feeder plate simultaneously and are wedged in the separation gap, with operational disruption and unnecessary down time being the result. Variations in the thickness of the blanks may occasionally make it difficult to place the blanks in the correct position at the discharge end of the magazine, and so it also happens that the feeder plate passes the magazine without entraining a blank at all.
Another factor which gives rise to uncertainty in the discharge of blanks using prior art apparatuses is the friction between the individual blanks loaded in the magazine. One basic precondition for a blank to accompany the feeder plate is, of course, that the blank lies flat against the plate, and in order to ensure this, a relatively high pressure is applied against the opposite end of the row of packaging container blanks. As a result, the friction between the blanks will be extreme and the separation force increases, which may result in deformation of the blank when it is to be picked by the feeder plate.
Thus, there is a need in the art to provide a discharge apparatus which, with considerable reliability, can discharge one blank at a time irrespective of any possible variations in the quality or thickness of the blanks, or in the discharge force required from the magazine.